Process for dewaxing oils



March 26, 1940. U BRAY El' AL PROCESS FOR DEWAXING OILS original Filed March :51, 1936 Weary 012 I Pro ane Soage 5 F9850?" p l 29 6 Cooler Chillers 51a l fvapora or 84- fvaparaiors 5 7 IN VEN TORS Ziria D. Bra

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A TTORNEY.

Patented Minze, 1'940 UNITED. STATES.:

`2,194,969. 'f PRooEss Fon nEWAxING oms j lUlric B.- Bray, Palos Verdes Estates, and Joseph A. Campbell, Jr., VManhattan Beach, Calif., as-

signors to Union Oil .Company of California, Los Angeles, Calif., a. corporation of California Original application March L ,1930, Serial No. l71,921. Divided and this application-Aprilh'ZZ,

`is caimsl (c1. ieee-is) The present invention relates to a process for the separation of lwax from oill,l 'Ihe invention also relates to the -fractionation of wax separated'from oils toy p-roduceboth high and low 5 melting point waxes.- The invention particularvly relates to a processforseparating high melting point wax from oil or from a mixture of low and high melting point waxes by a process corresponding to a leaching out of-the oils and soft waxes by means of a suitable solvent from lsolidi- `fied discrete particlesof oil, soft and hard waxes,

f the discrete particles being produced by contact` of themixture with the cold leachingsolvent at a temperature at which the soft .wax .and oil is i soluble in the solvent but the ha'rd Wax is insoluble therein. "I'his invention is a division of our co-pending lapplication Serial No.` 71,921, led March 31, 1936. i

It has heretofore been-proposed to separate wax from oils in thepresence of ja diluent, preferably a liquefied normally gaseous hydrocarbon, such as liquid propane." In this process, the waxy oil is dissolved inthe liquid propane under supei-atmospheric pressure and the mixture is chilled by reducing the pressure and vaporizing a portion of the solvent. By reducing the pres- I sure to substantially atmospheric, temperatures as low as 40 F. may be obtained. The chilled mixture is then filtered, centrifuged or cold set-A tled to remove the wax from the chilledvmixture. The foregoing process of separating wax from oil is commonly referred to as the solution and precipitation method for dewaxing oils.

It has also been proposed by Bray, applicant for patent Serial No. 745,417, filed September2`5,

. 1934, to separate wax from oil by a process corresponding to leaching of the oil from solidified wax structures. In this process, the waxy oil is sprayed into a body of cold solvent or diluent` which l'is maintained at a wax crystallization H temperature, say -40Q F., whereuponthe waxy l oil is crystallized or solidified to form a plurality of congealed or solidified particles of` oil `and wax. Upon continued contactA of the solidified y 451 waxy oil particles, such as thai-.which takes place when these particles settle to the bottom of the container of chilled solvent, solution of the oil in the resulting solventtakes place leaving Wax' matrices undissolved. This processis commoniy 50 referred to as the colduleaching method; for 'd'e-v waxing oils.

In either of the above processes, when operat ing atk a temperature of 40 F. which is apparently'necessary in order to produce lubricating 55 yoils ofllow pour test,-the wax cake contains a solvent.

Wide variety of paraiins as regards their meltl ing point.' In other words, the wax 'cakefcon tainsqnot only the high melting point normal straight chain parafiins but also the lower melt#` ing point parains having varyingrv degrees of ".52 iso-parain characteristics. It' has been found that the low melting point -iso-paraflins must be removed from the lubricating oil in orderY to oli#` tain an'oilof satisfactorily-low pour point'.` "We havegnow found that these low melting point 10" isoparaiflns must als'obe removed from the wax cakes ybefore they latter canbe'used forfvma'ny. commercialpurposes. In other words,` itis not only necessary to deoil the'wax cales completely` in theusual'se'nse of the word corresponding to 15 the'removal of vall the lubricating oil `fractions f which are definitely liquidyat say 30 F., but vitis Y at higher temperatures. In reworking such waxes,

use is made of such solvents at such pressure and" temperature yconditions that not only the oil v contained in the wax mixture" is soluble, butthe lower melting-point waxes or iso-parafns would 30 alsobe soluble to any desired degree. We have found the liquefied normally gaseous hydrocarbons to be particularly useful in thisv connection. Such solvents include ethane, ethylene, propane,` i propylene, butane, butylene, iso-butano and 35 mixtures thereof.I The Vcold leaching method aforementioned is particularly adapted yfor the fractionation 'of waxes. With the use of the aforementioned solvents, the variation of the temperature of leaching` may be accomplished 40 by means'of variation of :pressure on the volatile For example, propane held under `a pressure of about 30 lbs. per square inch has avg, temperature'of about 20" F. which is aysuitable temperature for the fractionation of some waxes. If l desired,`v a volatile solvent or a mixture of volatile solvents may be employed as thev leach-*- ing solvent whichhas a boilingpoint at'atmospheric pressure of approximately the vdesired temperature of. leaching. For example, `Com- 60,

sure. Y -55 l We have also discovered that the mixture of.

waxes containing considerable amounts of lubricating oil, such as a waxy lubricating oil dismelting point wax and a lubricating oil of low i pour point in a simple, economical and efficient manner. Thus, instead of separating a mixture of low and high melting point wax from the original oil containing the same at a low temperature vof say 40 F. and then fractionating the separated waxes into high and low melting point waxes, we have found it possible to subject the original stock to cold leaching in a suitable solvent in accordance with the method hereinafter described at a temperature at which the oil and soft waxes or iso-parains which are soluble in the leaching solvent but in which the high melting point waxes are insoluble. In this process, a separation is made of the high melting point waxes on one hand and the soft wax and lubricating oil dissolved in the solvent on the other hand. The solvent solution of the low melting waxes and oil separated from the high melting point waxes at a temperature in which such waxes are insoluble is then further chilled to precipitate the soft waxes which may be separated from the solution of oil and solvent by any convenient method such as by filtration, settling oricentrifuging. When this process is employed, a greater advantage is obtained not only in the improvement obtained in the operation of the process with regard to filter rates and lter operation but that a large percentage of the cost of chilling is eliminated. Thus, when a liquefied normally gaseous hydrocarbon is employed as the diluent-refrigerant for separating the mixture oi waxes from the oil to produce a' lower pour point oil and for treating the separated mixture of waxes in order to remove the high melting point wax, the cost of reliquefying the gaseous hydrocarbon by compression and condensation represents a material proportion of the cost of operating the entire system. Not

only does this cost represent a considerable proportion of the operation of the system but it requires the use of large expensive compressors for recovering the gas anda duplication of refrigeration and auxiliary equipment and also necessitates provision of large storage capacity for the diluent-refrigerant.

Thus, in the operation of the process forming the subject of our invention, it will not be necessary to subject the separated mixture of high and low melting point wax to fractionation in a solvent. .It is merely necessary to subject the original stock to a leaching operationl at a controlled temperature to separate the high melting point waxes and then further chill the solution containing the soft waxes by evaporating a portionl of the solvent under reduced pressure to obtain a lower temperature sufficient to precipitate the softer waxes. This `combination of the cold leaching process followed by precipitationof the remaining wax avoids duplication of auxiliary equipment and also the refrigeration required for the dewaxing operation is advantageously employed for the operation of the wax-leaching unit making it unnecessary to provide duplicate refrigeration equipment. However, it will be understood that the fractionationv by leaching of the mixture of high and low melting point waxes which have been separated from oils at temperatures suiiicient to separate both types of waxes as a mixture is also within the scope of our invention.

It is therefore an object of our invention to fractionate a mixture of high and low melting point waxes into a low melting point wax and a high melting point wax. Itis a further object of our invention to accomplish the fractionation by a leaching process in a suitable solvent, particularly a liquefied normally gaseous hydrocarbon which is Mmaintained at a suitable temperature so that the fractionation of the waxes may be accomplished.

It is a further object of 'our invention to introduce a wax-oil mixture into a cold leaching solvent maintained at a temperature so that the softwax and oil are dissolved in the solvent while the hard or high melting point wax remains insoluble in the `cold`solvent, in separating the solution of soft wax, oil and solvent from the hard wax, in `chilling the last mentioned solution to a low temperature suicient to precipitate the softwax,` in sepa-rating the precipitated soft wax from the solution of oil and solvent and in separating the solvent from the oil.

Other lobjects and advantages of our invention will be apparent fromthe following description of the invention taken from the drawing which is not to be considered as limiting the invention.

In the foregoing description of the preferred embodiment, the use of commercial propane asa combined diluent and refrigerant has been described. However, it should be understood that other liqueed normally gaseous hydrocarbon such as ethane, ethylene, propane, propylene, butano, isobutane, butylene, etc., may be used separately or in admixture with each other. Instead of using liqueed normally gaseous hydrocarbons other normally gaseous diluent-reirigerants may be employed such as methylether, methyl chloride, dichlor-diluor-methane. Also admixtures of the foregoing normally gaseous diluent refrigerants and normally liquid hydrocarbons, such as gasoline, casinghead gasoline,

ynaphtha, normally liquid anti-solvents for wax such as acetone, acid esters, mixtures of benzine with naphtha, mixtures of acetone and benzol, andthe like, may be employed. If desired, the normally liquid hydrocarbons such as pentane and hexane may be employed as the leaching solvent. These may be chilled by external means as is well known by those skilled in the art. In the preferred embodiment practically complete separation of the wax from the oil is effected by the useoi commercial propane as the diluent refrigerant.

Referring to the`drawing, a waxy stock such as a S. A. E. 20 distillate produced bythe vacuum distillation of a Santa Fe Springs crude is drawn from tank l via line 2 and pumped by pump 3 through line 2a controlled by valve 3a through` spray head Lin, into the rst leaching column or extractor A. The leaching column is first iilled with a cold leaching solvent, for example liquid propane at an appropriate temperature sufiicient to dissolve the oil and low melting point isoparafn type waxes which may be at a temperature of approximately 10 F. to 40 F. which represents the temperature in which the oil and soit waxes are soluble in the cold leaching solvent but only small amounts of the harder or high melting point Wax are soluble in the solvent.

Filling of the leaching column is accomplished by withdrawing liquid propane from propane storage tank under superatmospheric pressure at about normal temperatures and passing it via vinto propane Chiller 9 where a portion of the propane is vaporized by opening valve lIl on line I0. The vaporized propane being released through valve II passes through line I to compressor l2 where the propane vapors are compressed which then pass vthrough line I4 to condenser I5 where the compressed vapors are reliquei'led and returned to propane storage tank 5 via line i6. By reducing the pressure in Chiller 9 to approximately 20 to 65 lbs. per square inch,

the temperature oi' the remaining propane will be lowered to approximately 10 F. to 40 F. The chilled propane. is withdrawn from the bottom of Chiller 9 via line I'I controlled by valve I8 and is passed by pump I9 into the rst leaching column A via lines 20, a controlled by valve 2Ia and line 22a controlled by valve 23a.

When the required amount of propane has been introduced into the leaching column A, the waxy oil at an appropriate temperature is sprayed into the Vessel. The temperature at which the waxy oil is heated prior to spraying it into the cold leaching solvent will depend upon whether it is desirable to solidify the sprayed waxy particles `in the form of Cornflakle-like shapes or as pellets, discs or strings when the waxy oil is contacted with the cold leaching solvent. 'We have found it desirable to eect the solidication of the sprayed waxy oil droplets as cornflake-like shapes since it requires less time for the leaching solvent to leach the oil from the solidied wax structures although the solidification as pellets, discs or strings is within the scope of our invention. The solidication of the waxy oil in the cold leaching solvent as cornake-like shapes may be accomplished by rst heating the waxy oil so thatitassumes the viscosity of 350 seconds Saybolt Universal and then spraying the waxy oil through a spray head provided with a large number of small nozzles. The introduction of the waxy oil into the cold leaching solvent at a viscosity above 350 seconds Saybolt Universal results in the solidication of the waxy stock upon contact with the solvent as pellets, discs or strings. For the S. A. E. 20 waxydistillate obtained from the Santa Fe Springs crude oil, it has been found that the desirable temperature Vof heating prior to the sprayingis about F. or 120 F. For an S. A. E. 50 stock the temperature should be about F. 'Ihis temperature, of Course, will vary with other waxy stocks. Also, the temperature of heating will depend somewhat upon the size of the nozzles employed in the spray head as will be readily understood by those skilled in the art.

We have obtained good results when'using liquid propane as the leaching `solvent with as low as three volumes of the propane to one of the waxy oil in the initial leaching column A. However, by employing larger amounts of propane, say l0 volumes of the propane to one of the oil, the leaching of the oil from the solidified particles of oil and wax will take place more rapidly and also less foaming will be encountered during the addition of the last part of the waxy oil. However, it is not economically desirable to employ more than 10 volumes of propane'due to the large capacity of the leaching columns required to effect the leaching operation and the cost of the chilling and due also to the cost of chilling and recovering additional solvent.

It will be observed thaty when employing a liquefied normally gaseous hydrocarbon, such as liquid propane, as the leaching solvent, a portion of the solvent will vaporizeimrnediately upon contact with the relatively warm waxy oil thus creating a turbulent condition in the column, This is not ldesirable since the leached wax matrices being fragile are readily disrupted by any substantial agitation into nely dispersed wax particles which aredi'icult to separate from the oil solvent solution. It is therefore preferable to maintain quiescent leachinghconditions and to prevent substantial boiling in the leaching column. This may be accomplished by controlling the vaporization of the solvent in the columns or by maintaining pressure therein. `The pressure may be controlled by means of valves 85a, 85D, 85C, 85d, on lines 86a,y 86h, 86C, 86d, respectively, of leaching columns A, B, C, D, respectively. If desired, an extraneous gas, such as air, Carbon dioxide `or other non-miscible gases may be introduced into the columns to create a pressure therein and vsuppress boiling. Also, in the case where a liqueed normally gaseous hydrocarbon is employed asa leaching solvent which has a vapor pressure greater than atmospheric at the leaching temperatures, valves 85a, 85h, 85e, 85d, on lines 86a, 86h, 86o, 86d, respectively, are employed `for maintaining the pressurein the columns so that the desired ltemperature may. be maintained in the leaching columns. It is also desirable to preventinltration of heat from the outer walls of the leaching columns since this causes propane to boil therein. One method for preventing this is to jacket the outer walls ofthe columns and to circulate a cold medium through the jacket. y

The waxy stock is allowed to remain in contact with the leaching solvent for a period of time, say l5 minutes to 2 hours, to allow a substantial quantityof the oil occluded in the Wax matrices to be leached by the solvent. 'At the end of the leaching period, the fresh propane is introduced at the top ofr the vessel from propane Chiller 9 and valve- 23his opened and the solution is drawn oil from the iirst leaching column A and is transferred by pump 58a through lines 24a, 25a and 22h into the second leaching column B. The introduction of solution of oil and solvent into-the second leaching Acolumn B is Continued until substantially all of the solution in column A is displacedA with fresh propane whereuponA waxy oil from tank I is sprayed by line 2b' controlled by valve 3h through spray head 4h, the introduction of waxy oil being continued until the required amount of oil has been introduced into the column B. In the meantime, the wax structures in col-- umn A are subjected to leaching with fresh solvent which lowers the oil content ofthe wax structures. When suicient leaching timeh'as been allowed in column B, the oil propane lsolution is transferred via the bottom of the leaching column B by pump 58h through lines 24h, 25h and 22e controlled by valve 23C into the nal leaching column C. Simultaneously therewith,

The displacement of propane oil solution in l leaching ,column A is repeated a number oi times, depending upon the total number or" stages or extraction ,vessels in the system, say threeas shown in the drawing, until substantially oil-free propane is withdrawn from the bottom of the leaching column. The oil propane solution is then Withdrawn from the bottom of the last leaching stage C via pump 58e and lines 24e and 2'lc controlled by valve 28c'and is passed through line 29 to either of the alternate Chillers 3l and 33 via either line Si) controlled by valve 33a or line 32 controlled by valve 32a. If desired, filter aid may be introduced via line 29a into line 29 to mix with the solution passing to the Chillers. The solution in Chillers 3| and 33 is further chilled to a temperature sufciently low to precipitate substantially all of the-remaining wax contained therein, preferably by gradually reducing the pressure to substantially atmospheric by operation of valves Sila and 35a. on lines 313 and 35 respectively. This causes propane to be vaporized which chills the remaining solution to the desired dewaxing-temperature, the propane vapors being withdrawn via line 34 or 35 depending upon which of the Chillers are in operation. The vapors then pass into line 35, are compressed by compressor 3i and are returned to propane storage tank 5 via line 3S, cooler l5 and line l. Chilling is preferably accomplished at a rate not in excess of substantially 3 F. per minute.

The chilled oil, propane and wax slurry is withdrawn from thebottom of the Chillers 3l and .'33 via lines 3E and Mi, respectively, which are controlled hy valves 39a. and 46a, respectively, the mixture then passing into line ll is pumped by pump til* through line d3 to lter 44 Where the wax precipitated from solution by chilling is separated from the oil and solvent. vThe clear solution is then passed through line 45 through heat exchanger 46 where the temperature of the clear solution is raised to a temperature suiicient to vaporize the propane, after which the pre- ,heated solution is passed through line 41 into evaporator 4S. l'ihe propane is vaporized from the oil in evaporator i8 aided by steam circulated through closed coil 49, the vapors passing through mist extractor 5t and are Withdrawn Va line 5l controlled by valve 51a and are sent to propane storage tank 5 Via cooler 52, lines 53 and l0, compressor l2 and condenser l5. The dewaxed oil is withdrawn from the bottom of the evaporator via line 54 and is pumped by pump 55 through 'valve into dewaxed oil storage tank 51.

The separated wax in filter 44 is withdrawn via line 13 controlled by valve 13a and is passed through heat exchanger 'M and line 15 into evaporator 1li provided with closed heating coil Vl and mist extractor 18 in which the wax is depropanized. The depropanized low melting point wax is withdrawn from evaporator 16 via line 80 and is pumped by pump 8l through valve 82 into storage tanl; 83. Propane vaporized in evaporator 'l5 is withdrawn via line 19 controlled by valve 79a and passes via line 84 into line 5l.

As stated above, when substantially all of the oil and soft wax or iso-parans have been leached from the wax matrices with fresh propane in the rst leaching column, the latter is cut out of the system and the fresh propane is introduced into leaching column B which then becomes the iirst leaching column in the system. Leaching column D is then cut into the system by lling the vessel with propane oil solution withdrawn from leaching column C via lines 24e, 25C and 2id controlled by valve 23d. This, of course, is accomplished until the solution in column B has been displaced with fresh liquid propane. Waxy oil is then sprayed into column D via lines 2 and 2d controlled by valve 3d and spray head 4d. As in the case of column A, when the leaching operation in column B is substantially completed, the propane oil solution in column D is passed to the Chillers via lines 24d, 21d controlled by valve 28d, line 29 and either line 3B or 32. The propane solution from column B is then transferred to column C and thence to column D, fresh propane being introduced into column C via line 20c controlled by valve Zlc and line 22e controlled by valve 23C. Column C then becomes the iirst leaching column, column B the second leaching column and column A after removing the wax therefrom becomes the third leaching column.

We have thus described a process for separating wax from oil involving leaching of the Wax structures wherein a plurality of leaching columns are provided so interconnected that the flow from one leaching column may be diverted from one to the other and the leaching columns are so interconnected that they may be rotated in such manner that a semi-continuous operation may be carried out with the use of an extra leaching column. Also, in the above description, discontinuous batch leaching is shown. However, the invention is not to be considered as limiting thereto since it embraces continuous flow of leaching solvent from one column to another, that is, the operation may be carried out in such manner that fresh' propane is continuously introduced into the rst leaching column and concentrated propane oil solution containing iso-parains or soft wax is Withdrawn from the last leaching stage and passed to the Chillers. Thus, we may operate in such manner that the oil solvent solution and soft wax may be continuously passed to the Chillers. The production of the oil propane solution from the last leaching column is controlled by time, for example, if approximately one hour is calculated from the rate of flow of wash propane in the system to be required for displacing the propane oil solution in any of the leaching columns, then the first hours withdrawal of propane solution from the vessel just charged with oil is sent to the Chillers. The propane solution withdrawn subsequently is then used as wash propane in the second leaching column. If in charging an empty leaching column for a new cycle, all of the propane solution required for leaching and washing the waxy stock for the iirst time is accumulated in the leaching column before introducing the waxy stock, it is desirable, although not necessary, to interrupt the ow of wash propane While the waxy stock is being introduced. giving periodical interruptions in the flow of both wash propane and propane oil solution. To avoid interruption in the flow of wash propane, the introduction of waxy stock into the fresh or empty leaching column may be begun after only a part of the propane solution required for filling the leaching column is introduced and the rate of addition of waxy stock be adjusted so that the addition of waxy stock is completed by the time the liquid reaches the proper level.

In order to minimize the amount of entrained wax particles in the solution withdrawn from the bottom of the leaching vessels, filter beds 590., 5917, 59e, 59d, are provided at the bottom of the leaching vessels to hold the leaching wax structures in the column while the propane solution is allowed to Wash through it. For this purpose, any desirable material may be provided, such as pads of steel wool, broken glass, stones, pebbles,

tor is cut out of the system, the wax structures are then removed from the leaching column and are distilled to recover the wax and solvent. The removal of the wax structures maybe accomplished by introducing a warm liquid into the leaching columns via lines 65a, Gill), c and 60d to partially or totally melt the wax structures,

the melted wax being withdrawn from the bottom of the leaching columns by pumps 58a, 58h, 58o, and 58d, and valves Gla, SIb, Bic, and Gld respectively, and passed into line 62 controlled by valve 62a to heater 63 where the structures are heated to a suflicient temperature to vaporize the propane after which the mass is passed through lines 64 into evaporator 65 where the propane is vaporized from the wax aided by steam circulating through closed coil 6B, the vaporized propane passing through mist extractor 51 into line E8 controlled by valvea. The high melting point wax withdrawn from the bottom of the evaporator $9 is pumped by pump 1G through valve 'H into high melting point wax storage tank 12. This wax may be further treated such as with sulfuric acid and alkali and/or clay to produce a high melting point Water white Wax suitable for the production of candles and the like.

In another method for removing the wax from the leaching column the wax structures may be partially disintegrated by mechanical agitation such as by means of Scrapers or stirrers built into the leaching columns or by blowing the structures with propane or other gas. The mass may be transferred from the bottom of the leaching column by means of a screw conventor or transferred as a slurry by pressure, the slurry being produced if desired, by mixing the wax with propane to form a pumpable mass. yThis mass may be ltered, centrifuged or settled to concentrate the wax particles and recover chilled propane suitable for Washing other wax structures. The concentrated wax or wax cake may be Washed with further quantities of fresh pro-` pane to reduce the oil content still further. The use of a continuous oil drum type filter is preferred for `washing and iiltering the wax taken out of the leaching columns. The wash propane may be employed for washing other wax structures in keeping with the spirit or the invention.

When employing filter beds in the extraction columns, the wax structures may be removed by first withdrawing as much of the liquid, propane as possible through the filter bed without however bringing the liquid level below the top edge of the filter bed. The filter is then back blown with propane gas and additional wash propane is introduced at the bottom of the iilter bed. The back blowing washes wax out of the ilter bed into the wax slurry on the top. The back y blowing can be very violent, if desired, in fact so violentthat the entire filter bed is blown up into suspension along with the wax in the propane liquid which will have now been brought to a convenient height in the extraction vessel. Upon stopping the violent agitation by blowing the heavy filter bed material will settle with extreme rapidity leaving practically all of the wax suspended as a slurry in the propane phase which can then be decanted oil? ata point `iust above the top of the lter bed. In this manner the filter is then cleaned and ready for another cycle. In

`or a waxy petroleum residue.

beginning afresh"cyclethev rst production may be recycled if cloudy.

The foregoing invention has been described as used for the separation of wax from an S. A.1E 20 lubricating oil distillate producedv from Santa Fe 5 Springs crude petroleum. It should beunderstood,

however, that the invention is equally applicable for the separation of waxfrom' any wax-bearing oil whether it consists of alubricating oil distillate Thel invention is also applicable for the fractionation of waxes containing only a small amount of oil such as slack kwaxes which have been lseparated from petroleum fractions.

In some instances, we find it desirable to introduce the wax-oil mixture linto the cold leaching solvent as a nely divided solid. 'I'he wax-oil mixture may be solidified by lowering its tem` perature to produce a solid mass which can then be mechanically broken up byany suitable-means 20 into ribbons, strings, or irregular shaped particles which could then be mechanically introduced into the cold solvent. It is desirable to break the mass into such particles that the solvent need not penetrate over` 143th 'inch sections and preferably not 25 over lgth inch sections. as sections thicker than this do not leach within areasonable length of time.`

There are several methods which are applicable forsolidification and break-up of the oil-wax mixture. One method involves the solidiilcation ofthe oily and wax mixture yin blocks orrrods lwhich is then broken up by slicing oi thin wafers by means of warmed knives, similar to a butchers slicing machine.` f

In another method, the wax-oil mixture is maintained in a trough in a fluid condition by heating, if necessary. A chilled cylinder is al-` lowed todip into the liquid which is rotated at such a speedthat a lm vof solidified wax-oil mix- 40 ture of the desired thickness of Mgth to th inch is deposited on the cylinder. This lm may then be removed by a scraper 'to produce akes of the solidified material which can then be fed into vthe cold leaching solvent. i s ,45

In another method, the oil-wax mixture is' chilled to a temperature below the ordinary solid- .ification point but still the .temperatureis suffl- `ciently high that the mixture can be mechanically worked or kneaded into a plastic condition. 50 'This plastic material is -then extruded through gree of chilling controlled to obtain the desired i plastic condition. Mechanical devices for chill 05 ing the Wax-oil mixture below itsy solidiflcation point and at the same time keeping the chilled material plastic by mechanical working are well known to those skilled in the art, and therefore need not be fullydescribed herein. s f' U The introduction of the wax-oil'mixture as a free-falling stream at a sufficiently-high temperature that it is liquid, has beenv described above. However, in some instances it is desirable to adjust the temperature of the wax-oil mixture prior 7.'

toits introduction as near the solidication point of the particular oil-wax mixture as possible.

If desired, the liquefied oil-wax mixture and solvent may be introduced simultaneously as impinging sprays in the vapor spaces of the leaching vessel and then allowed to fall together into the liquid in the vessel. The solvent may be introduced either in a pre-cooled condition or when a liquefied normally gaseous hydrocarbon is employed, it may be introduced under pressure and allowed to expand in direct contact with the oilwax mixture. In the latter case, the expansion of the liquefied normally gaseous hydrocarbon results in a vaporization of a portion of the solvent and thus chills the remainder of the solvent and also the oil-Wax mixture. The length of fall is preferably sufficient so that the oil-wax mixture is solid when it iinally comes to rest in the vessel. When using a liquefied normally gaseous hydrocarbon as the leaching solvent, solidification takes place so rapidly as to be practically instantaneous. The oil-wax mixture should be sprayed through small orices so that the resultant solidified particles present sections leth to 1/gth inch. This method of operation has the advantage of asaving in charging time when used in the countercurrent downflow leaching.

There is a tendency when employing certain solvents for the solidified oil-wax mixture to float on the solvent for such a length of time that there is a serious loss of time efficiency in charging the wax-oil mixture to the leaching vessel. This difiiculty may be overcome by gentle mechanical agitation of the solidied particles in the leaching vessels such as by means of stirrers or a portion of the solvent or solvent and oil from the bottom of the leaching vessel may be recirculated so that a stream of the liquid is lcontinually sprayed over the surface of the oil-wax mixture in the leaching vessel. This will enable the solidied wax-oil particles to settle to the bottom of the vessel.

In some cases it is desirable to introduce other materials into the oil-wax mixture for the purpose of strengthening the solidified particles. We have found this to be particularly desirable in oil-wax mixtures of low wax content. We have found that when the wax structure after the removal of the oil or oil and soft waxes represents less than 12% to 15% by volume of the original wax-oil mixture, it is very thin and tenuous and is easily crushed by the weight of the wax above it, or it is broken up by boiling or by eddycurrents of the solvent. When broken up, the wax structure settles and becomes compacted into an impervious mass which retards or prevents further leaching. We have found that the addition of other materials to the wax-oil mixture before solidiication will prevent this occurrence. For this purpose we may use materials which have heretofore been used to improve ltration characteristics of the chilled mixtures containing preciptated wax. Such materials include asphalt, cracked petroleum residues, oxidized wax and the like. In some instances we find it desirable to increase the wax content of the particular wax fraction desired to be removed by leaching so that the wax content represents at least 12% to 15% by volume of the wax-oil mixture introduced into the leaching` vessel` These materials may be added to the waxy oil via line ia. If desired, emulsied water in the oil-wax mixture may be used for strengthening the wax structures. If desired, the laying down of alternate layers of solidified oil-wax mixture and ice, asphalt or sand or the random mixture of the solid particles of ice, asphalt or sand in the solidiiied oil-wax mixture in the solvent may be employed.

The separa-tion of the added asphalt and the like from the wax after leaching may be accomplished by breaking up the leached structures after the desired degrees of leaching has been accomplished. This may be done either in the leaching vessel or in a separate container but preferably in the latter. The mixture may be heated to a temperature which is sufficiently high to dissolve all the wax and allowing the mixture to settle. The asphaltic materials or oxidized wax andthe like present will then separate out either in a liquid or solid phase and are separated from the wax by decantation or iiltration. If desired, the wax slurry as removed from the bottom oi the extraction vessels may be heated without rst removal of solvent and the heated mixture then passed to a quiescent zone under pressure where the asphaltic bodies will settle out.

rIo illustrate the advantages obtainable by carrying out the process of extracting wax from oils forming the subject oi our invention, the following is submitted which, however, it is not to be considered as limiting our invention.

An S. A. E. 20 waxy distillate obtained from a Santa Fe Springs crude oil is first enriched with about 8% by volume of hard wax previously obtained from the same stock and is then heated to a temperature of about F. or about 20 F. above its pour point so that the waxy oil has a viscosity ci about 350 seconds Saybolt Universal. The preheated waxy oil is then sprayed into three leaching stages in accordance with the foregoing disclosure. Propane at about 20 F. and maintained under pressure of about 30 lbs. per square inch is employed as the leaching solvent. The initial ratio of propane to oil employed in the first stage of leaching was approximately 5 volumes oi' propane to one of the waxy oil, and the total amount of propane passing through 'the leaching vessel for complete extraction of the charge was 15 volumes based on original charge of waxy oil. The propane oil solution withdrawn from the bottom of the first stage was employed as leaching solvent in the second stage and that withdrawn from the bottom of thesecond stage was employed in the third stage. In the subsequent leaching stages the pressure and temperature conditions were maintained substantially the same as that maintained in the rst leaching stage. i The propane-oil solution from the third stage of leaching, corresponding to the third use of the propane, at atemperature of about 20 F., was further chilled by evaporative refrigeration, that is, by vaporizing propane from the chilled mixture at a rate not substantially greater than 3 F. per minute until a temperature of 40 F. was attained in the chiller. The chilled mixture was then filtered to remove the soft wax which precipitated upon chilling. Upon completion of the run approximately 75% of dewaxed oil was produced having a pour point of 5 F. The high melting point Wax was recovered from the leaching columns, after depropanization, had a melting point of F. and represented approximately 16% of the enriched waxy oil. Approximately 17% of the soft wax was recovered by further chilling the propane-oil solution from the leaching column and had a melting point of 100 F.

The high melting point wax was then treated at a temperature of about F. with about 25 lbs. of 100% HzSOi per barrel of the melted wax. f3

arredato not substantial. quantities of `hard wax, extract-l at an elevated temperature..-,In most cases it is not necessary to treat the acid treated wax or wax solvent solution with alkali when clayv treatment is employed although vthis may be employed.

The foregoing description of our invention is not to be taken as limitingl since many 'variations may be made within the scope of the following claims by those skilled in the art withou departing from the spirit thereof. l

We claim: l. A process for separating wax from a wax-oil mixture which comprises introducing the Wax-oil mixture into a solvent maintained at a temperaturesufcient to dissolve oil and soft wax but incapable of dissolving substantial amounts of4 the harder waxes, solidifying said wax-oil mix ture by contact with said solvent and allowing said solidied wax-oil mixture to remain in contact with said solvent for a suiicient period of time to permit said solvent to dissolve the oil and soft waxes, separating the solution of oil Vand soft waxes from the harder waxes.l

2. A process as in claim l in which the solvent is a liqueed normally gaseous hydrocarbon.

3. A process for separating wax from wax-oil mixtures' which vcomprises congealing a wax--oilr mixtiue by contact with a cold solvent capable of dissolving oil and a portion of theA wax content at low temperatures but incapable of dissolving all of thev wax content at the temperature employed, extracting the oil in said congealed waxy oil by means of said solvent. to leave awax matrix substantially free from oil and a portion of the oil solvent solution containing the soft wax to wax content, separating the wax matrix from the oil dissolved in said solvent, chilling said oil and solvent to a temperature lower-than the temperature of said cold solvent to precipitate further quantities of wax from the oil and solvent,

separating said precipitated wax from the oil and solvent and separating the oil from the solvent.

4. A process for separating Wax from wax-oil mixtures which'comprises congealing a wax-oil mixture by contact with a cold solvent maintained at a temperature sufcient to dissolve oil and soft wax but not substantial quantities of hard wax contained in said congealed wax-oil mixture, extracting the oil and soft wax contained insaid congealed wax-oil mixture by means of said solvent to leave a matrix of relatively hard wax substantially free from relatively soft wax and oil, separating the matrix of hard wax from the solution of oil and soft wax,- chilling the solution of oil and soft Wax to a temparature at which the soft wax is precipitated from the oil and solvent and separating said precipitated soit wax vfrom the oil and solvent.

5. A process as in claim 4 in which the cold solvent comprises a liquefied normally gaseous hydrocarbon.

6. Aprocess as in claim 4 in which the cold solvent comprises liquid propane.

7. A process for separating Wax from Wax-oil mixtures which comprises congealing a Wax-oil v mixture by contact with a cold liquefied normally gaseous hydrocarbon maintained at a temperature suiicient to dissolve oil and soft wax but ing the oil and soft wax contained in said congealed Wax-oil mixture by means of said hydrocarbon to leave a matrix of hard wax substan-` tially free from oil and soft wax, withdrawing the solution of oil and softwax `from the matrix ofr hard Wax, vaporizing a portion of the hydrocarbon from the solution of oil and soft wax to 1 chill said. solution to a lower temperature and thus precipitate said soit wax, separating said precipitated soft wax from .the oil and hydrocarbon and separating said vhydrocarbon from' said oil.

` 8. lA processfcr separating wax from wax-oil l mixtures which comprises spraying a wax-oil mixture into `a liquefied normally gaseous hydrocarbon maintained at a temperature sufficiently low to dissolve oil and soit waxwbut not substantial quantities of hard Wax, solidifying said sprayed wax-oil mixture by means of said cold solvent to form a plurality of congealed particles .of wax and oil, extracting the occluded oil and ,mixture which comprises Acongealing a Wax-oil mixture by contact with af'solventy maintained` at a temperature of approximately 20 F., extract p v 'ing the oiland soft wax in said `congealed. .wax-l `oil mixture by means of said solvent at said Atemperaturetoleave a wax matrix substantially free from oil and soft wax, separating theoil and soit wax from lthe wax matrix, chilling the a temperature of approximately 40 F. to precipitate the soft wax and separating the `soft wax from the oil solvent solution.

10. A process as in claim 9 in which the solvent comprises a liqueiied normally gaseous hydro-` carbon. f

11. A process as in claim 9 in which the solvent comprises liquid propane` mixtures which comprisescongealing a wax-oil I mixture by contact witha cold solvent'mainl tained at a temperature suiiicientto dissolve oil and soft wax but notsubstantial quantities of hard wax contained in saidcongealed wax-oil mixture, extracting the oil and soft waxcone tainedy in said congealed wax-oil mixture vby means of said solvent to leave a matrix of rela'- tively hard wax substantially freefrom relativelyl soft waxland oil, separating4 the-matrix of hard wax 'from'the solution of oil and soft wax, treating said hard-Wax with acid and subsequently treating said acid-treated Wax with clay.

13. A process for separating wax from Wax-oil mixtures which comprises congealing a wax-oil mixture by contact with a cold'solvent `maintained at a temperature suicient lto dissolve oil and soit wax butnot substantial quantities of hard wax contained in saidcongealed wax-oil mixture, extracting the oil and soit wax contained in said congealed wax-oil mixture byl means of said solvent to leave a matrix of relatively hard Wax substantially free from relativelyl l soft Iwax and oil, separating the matrix of hard so 12. A process iorseparating wax from waxeoll y wax from the solution of oil and soft wax, heating said matrix of hard wax to melt the same, treating said melted wax with sulfuric acid 'at va temperature of about 175 F. and subsequently treating said acid-treated wax with clay lat a temperature vof approximately 250 F.

14. A process for separating wax from wax-oil mixtures which comprises congealing a wax-oil mixture contact with a cold solvent maintained at a temperature suflicient to dissolve oil and soft wax but not substantial quantities of hard wax contained in said congealed wax-oil mixture, extracting the oil and soft wax contained in said congealed wax-oil mixture by means of said solvent to leave a matrix of relatively hard wax substantially free from relatively soft wax and oil, separating the matrix of hard wax from the solution of oil and soft wax, commingling said solution of oil and soft wax with a small amount of a lter aid, chilling the mixture of oil, soit wax and lter aid to a temperature at which the soft wax and iilter aid are precipitated from the oil, and filtering said chilled mixture to separate the precipitated soft wax and lter aid from the oil.

15. A process for separating hard wax from a wax-oil mixture containing the same but in which the percentage of hard wax is less than 12% to 15% by volume based on the wax-oil mixture which comprises mixing said wax-oil mixture with a suicient amount of hard wax to increase the hard wax content of said mixture to approximately 12% to 15% by volume, introducing the wax-oil mixture into a solvent maintained at a temperature suicient to dissolve oil and soit Wax but incapable of dissolving substantial amounts of the harder waxes, Solidifying said wax-oil mixture by contact with said solvent and allowing said solidilied wax-oil mixture to remain in contact with said solvent for a sufiicient period of time to permit said solvent to dissolve the oil and soft waxes, separating the solution of oil and soft waxes from the harder waxes.

16. A process for separating wax from wax-oil mixture which comprises congealing a wax oil mixture by contact with a cold solvent maintained at a temperature suicient to dissolve oil and soft wax but not substantial quantities of hard wax contained in said congealed wax-oil mixture, extracting the oil and soft wax contained in said congealed wax-oil mixture by means of said solvent to leave a matrix of relatively hard wax substantially free from relatively soft wax and oil and separating the matrix of hard wax from the solution of oil and soft wax.

ULRIC B. BRAY. JOSEPH A. CAMPBELL, JR.

, Patent "No, 2,19ln969.

CERTIFICATE OF CORRECTION.

' March 26, 19m.

- ULRIC B. BRAY, ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as 'follows :l Page 8, first oolumn, line 6; claim l5, for "2500 F." read "5500. F'.; and that the said -Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

signed and sealed this 2nd day of July, A. D. 19m.

Henry Van Arsdale,

(Seal) Aoting Commissioner of Patents. 

